Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
s = [list(input()) for _ in range(H)]

total_white = 0
for i in s:
  total_white += i.count(".")

sh = 0
sw = 0
gh = H-1
gw = W-1

s[sh][sw] = 0
q = [[sh, sw]]
min_path = 0

while len(q) > 0:
  h, w = q.pop(0)
  if h == gh and w == gw:
    min_path = s[h][w]
    print(total_white - min_path -1)
    exit()
  for dh, dw in ([0, 1], [0, -1], [1, 0], [-1, 0]):
    if 0 <= h + dh < H and 0 <= w + dw < W:
      if s[h+dh][w+dw] == ".":
        s[h+dh][w+dw] = s[h][w] + 1
        q.append([h+dh, w+dw])

print(-1)